Your dad gets a tax waiver due to the fact that he is selling his primary residence. I assume he lived there for 2 years or more before going into the nursing home. The waiver is on $250,000 of “profit” so that would be over and above what he paid for it. If he paid $100,000 then he could sell for $350,000. Or if he has a mortgage obviously that has to be deducted.
He paid $20K back in 1963.